Project Summary Significance. Craniofacial microsomia (CFM) impairs facial muscle movement, speech, and hearing, and compromises socio-emotional development. Children with CFM have elevated levels of internalizing behavior (shy, withdrawn) and reduced social competence and peer acceptance. Unknown at present are the mechanisms through which CFM and these social-emotional outcomes become linked. Facial asymmetries and cranial neuropathies associated with CFM likely play an important role in impairing socio-emotional outcomes. Asymmetries of the facial skeleton, soft tissue, and cranial nerve have both intra- and interpersonal effects. Intra-personally, they impact function (unilateral hearing loss, malocclusion, facial expressiveness) and form (noticeable craniofacial malformations), which can impair social signaling and responsiveness. Because asymmetry is negatively correlated with attractiveness, there may be non-specific social effects as well. Many surgical treatments for CFM are designed to restore facial symmetry in static pose (e.g., neutral expression). Less is known about restoring or even measuring spontaneous facial expressiveness. From a developmental perspective, one of the most important consequences of limitations in facial muscle movement is its potentially negative impact on affective communication. In a longitudinal design, we propose to test the hypothesis that deficits in facial expressiveness and structural and functional asymmetry increase risk for internalizing and externalizing problems. If supported, the findings would inform our understanding of socio-emotional development in children with CFM and contribute to clinical evaluation and treatment. Innovation. This is the first effort to 1) use automated, objective measurement of facial expressiveness of communicative behavior and functional asymmetry of children with CFM; 2) model change with development in these parameters and their relation to internalizing and externalizing problems; and 3) use machine learning to investigate the relation among dynamics of expressiveness and asymmetry in relation to CBCL. Approach. Children with and without CFM will be video-recorded at 1 and 3 years with an examiner. Age 1 is an interactive context intended to elicit positive and negative emotion. Age 3 is an interactive context to assess expressive speech and attention. Expressiveness and structural and functional asymmetry are assessed using automatic, objective computer-vision based measurement. Analyses include complementary approaches: statistical (regression and ANOVA) hypothesis testing and machine learning (convolutional neural networks). Relevance Using objective, automatic computer-vision-based measurements, we propose to test the hypothesis that deficits in facial expressiveness and structural and functional asymmetry among children with CFM increases their risk for internalizing and externalizing problems. If supported, clinical assessments of expressiveness and functional asymmetry could effectively target children for specialized interventions and be used to evaluate surgical interventions. Because the proposed procedures are cost effective, they could be applied in a wide range of settings to benefit children with craniofacial disorders and have applicability to other conditions and age groups in which facial expression is compromised (e.g., Mobius Syndrome, Bell's Palsy, injury/burns, and stroke).